Concrete inserts are used to connect items to concrete structures after the concrete has been poured and hardened. A typical use of an insert is to embed it in a concrete ceiling so that a pipe hanger or the like may be connected to the ceiling via the insert after the concrete hardens. The following description will discuss inserts embedded in ceilings although inserts may be embedded in concrete floors or walls.
Some prior art inserts are U-shaped sheet metal pieces with legs terminating in flanges that lie in a common plane and with a bridge between the legs having a hole in it through which a threaded fastener is inserted. An internally threaded coupling is positioned between the legs of the U-shaped piece to butt against the bridge and a threaded fastener is screwed into the internal threaded cavity of the coupling and locked in place with a nut that abuts the bridge. The prior art concrete inserts are usually made so that the threaded coupling is the same length as the legs of the U-shaped piece whereby when the insert is nailed to a wooden form for concrete and after the concrete hardens and the form is removed, the opening to the threaded coupling is in the plane of the concrete ceiling and the open end of the coupling is exposed after which a threaded rod may be placed in the open end of the coupling and an element such as a pipe hanger can be fixed to the ceiling by connecting it to the rod. Inserts of this nature are known, for example, those illustrated as item 276 on page 89 of the 1986 catalog published by KIN-LINE, INC. located at 6425 San Leandro Street, Oakland, Calif. 94614.
Many concrete floors and ceilings are formed using metal plate or decking as the concrete form. When metal decking is used as a form it is not stripped from the concrete slab after the concrete sets. Rather, it becomes part of the structure and as a consequence inserts do not extend to be flush with the bottom surface of the ceiling formed by the metal decking. To use the above-noted prior art inserts on a ceiling having metal decking requires expensive and time-consuming adjustments of the position of the coupling viz a viz holes punched in the metal decking, and further requires a coupling having a different length from those used with wooden forms to accommodate extending through the thickness of the decking. As a consequence, a contractor must maintain a supply of inserts for metal forms and for plywood forms, and different inserts for each thickness of metal form.